One of the endearing aspects of SPO is that players often have freedom of choice in how to play the game. This includes how a mayor develops a town and how the president plays their political role. To mimic real life, there are checks and balances in place for each role including the zoning and road building of each office. The strongest balance of each office is the voting power of the players.
However, as in real life, there are those who will use their political office for the betterment of the planet, towns and general play while there are those who will use their political office for self gain.
To restrict the powers of the political roles to such an extent as to prevent any abuse would greatly restrict each political role and the players choices. That being said, if a player holds a political office, and is using the powers of that political office to such an extent that undue harm is caused by players either within a town or on a planet, depending on the office in question, then that player would be consider cheating and would then be subject to the rules under the cheating header.
An example of this would include the use of zoning for self gain. A further example would include a president or minister having a store or factory within a town that gets zoned by a mayor and the player holding the political office then re-zoning their store or factory back into play without the mayor's position.
If you feel that a player is abusing their political office to the level that they are receiving an unfair game advantage then please report the situation as described under the cheating discussion.